An issue common to these onboard systems is that they should make it possible to collect the information necessary for maintenance, for the management of alarms and for various technical investigations.
In the new generation aircraft, these systems communicate with onboard data concentrators and/or centralized maintenance computers, usually situated in the avionics rack, making it possible to collect, centralize, analyse, summarize, archive and transmit the necessary information to the operators or engineers.
However, in the previous generation aircraft, there is no data concentrator, which prevents any in-depth investigation and results in a large number of healthy equipment items being removed, complex and costly maintenance operations and aeroplane delays. In these aeroplanes, the collection of the flight data is made particularly difficult by the lack of space in the avionics rack which is combined with the high sensitivity of the avionics systems to electromagnetic disturbances. In practise, the aim is to snoop on the avionics systems without disturbing their operation. This is why, in the previous generation aeroplanes, the data are collected only on the ground when the aircraft is no longer in operational service. Unfortunately, the data collected are generally very inadequate and do not make it possible to explain anomalies associated with the operational and/or environmental context of the aircraft.